CN214039819U - Measuring sleeve with slidable ring buckle - Google Patents

Abstract

The utility model discloses a measuring sleeve with a slidable ring buckle, which comprises a shell and a shell cover, wherein the shell is fixedly connected with the shell cover and is internally enclosed into an accommodating cavity; the spring barrel is fixedly connected to the bottom surface inside the shell, a spring is arranged inside the spring barrel, the spring is fixedly connected with a sliding ring buckle outside the spring barrel, and the sliding ring buckle can move relative to the shell; a flexible rule outlet is arranged on any side surface of the shell, and the flexible rule penetrates through the sliding ring buckle and then extends to the outer side of the shell from the flexible rule outlet; the contact position of the flexible rule and the sliding ring buckle does not fall on the tangent line of the flexible rule outlet and the central column; the opposite side of the side surface where the tape outlet is located is provided with a tape hook which can be detachably connected with a tape. The utility model discloses have and carry out continuous monitoring to trees diameter, can discern the small change of trees to and avoid producing the technological effect of improper restriction to trees growth.

Description

Measuring sleeve with slidable ring buckle

Technical Field

The utility model relates to a trees field of measuring, concretely relates to take measurement cover of slidable latch closure.

Background

In forest resource investigation, diameter is an important measurement data, and is one of basic factors for responding to quality and growth quantity of active wood. The tree diameter naturally contracts and expands when the trunk moisture changes, and in addition, the diameter also changes when the trunk has fixed carbon dioxide and then causes the tree to grow. The method has the advantages that the diameter of the tree is continuously monitored for a long time, the short-term diameter change, the long-term growth amount and the growth rate change rule of the tree can be known, and the method has important significance for forest cultivation, forest accumulation amount investigation and the like.

The most original, the most direct measuring method of trees diameter is that the manual work is measured with enclosing the chi, and this kind of traditional trees diameter measurement mainly adopts diameter to enclose chi and trees diameter slide caliper rule to realize, and these two kinds of instruments still all are artifical readings, have human error, consume time power, inefficiency, and the variable quantity of diameter can't be measured accurately to this kind of method of on the other hand, also is inconvenient to carry out continuous monitoring to trees diameter.

For the above technical problem, there have been proposed related solutions. The prior art with publication number CN 111692948A discloses a tree diameter monitoring device, which utilizes a fiber tape to pass through a tape outlet and be fixed on the other side of a shell to form a closed ring, the fiber tape is wound on a rotating gear, and drives the rotating gear to rotate when the diameter of a tree increases. In addition, the rotating gear is linked with the counting switch, and finally the collected data is transmitted to the server end by the control electric plate, so that the tree growth condition can be dynamically monitored, and the trouble of manual measurement is saved.

Because the power that expands when trees grow is little, current device is difficult to effectively discern this power, leads to trees to grow and takes place to cave in, the deformity by the influence of measuring part, can cause the damage of different degrees to trees, also can influence the accuracy of the data of collecting.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a take measurement cover of slidable latch closure has and continuously monitors trees diameter, can discern the small change of trees to and avoid producing the technological effect of improper restriction to trees growth.

The utility model discloses a realize that the technical scheme who takes of above-mentioned purpose does:

a measuring sleeve with a slidable ring buckle comprises a shell and a shell cover, wherein the shell is fixedly connected with the shell cover and internally enclosed to form an accommodating cavity; the middle part of the rotating part is provided with a central column, and a flexible rule is wound on the side surface of the central column; the spring barrel is fixedly connected to the bottom surface inside the shell, a spring is arranged inside the spring barrel, the spring is fixedly connected with a sliding ring buckle outside the spring barrel, and the sliding ring buckle can move relative to the shell; a flexible rule outlet is arranged on any side surface of the shell, and the flexible rule penetrates through the sliding ring buckle and then extends to the outer side of the shell from the flexible rule outlet; the contact position of the flexible rule and the sliding ring buckle does not fall on the tangent line of the flexible rule outlet and the central column; the opposite side of the side surface where the tape outlet is located is provided with a tape hook which can be detachably connected with a tape.

The utility model discloses in, the tape extends to the device outside from the tape export, encircles and is connected with the tape couple behind the trunk, through the tape, the utility model discloses can fix on the trunk surface, simultaneously, the trunk growth drives outside tape extension, therefore the accessible tape carries out the continuation to the trunk diameter and measures. The rotating component is mainly used for fixing and retracting the tape, and the rotating component and the shell can rotate relatively, so that the clockwise or anticlockwise rotation of the rotating component can realize the retracting function of the tape. The spring box and the sliding ring buckle fixedly connected with the spring form a reciprocating contraction mechanism, when the tape is influenced by the growth of trees and extends, the sliding ring buckle is driven to move, and the spring is further driven to contract, so that the resistance generated by the spring is required to be overcome when the tape is extended outside the shell.

Preferably, the two end faces of the central column of the rotating component are respectively provided with a first baffle, and the area of the first baffle is larger than that of the end face of the central column; a first baffle at the top of the central column is provided with a pawl part, the pawl part consists of a sliding block, a sliding way, a spring and a spring seat, the sliding block is movably connected inside the sliding way, the sliding block is connected with the spring seat through the spring, and the sliding block can move relatively on the diameter of the first baffle; the slide block is wedge-shaped.

The sliding block is wedge-shaped, namely, one end of the sliding block, which is far away from the center of the first baffle, is wedge-shaped, namely, an inclined plane exists, when the rotating component rotates, so that the inclined plane of the sliding block is contacted with another inclined plane matched with the inclined plane, the sliding block can move to the center of the first baffle along the slide way, the spring is compressed, and when the sliding block passes through the other inclined plane, the sliding block can reset under the action of the spring.

Preferably, the shell cover is provided with a ratchet component, the ratchet component comprises a second baffle plate, the bottom of the second baffle plate is fixedly connected with at least one ratchet, and the ratchet is annularly and uniformly distributed by taking the axis of the central column as the center; when the spring is in a free state, the sliding block is meshed with the ratchet; the pawl component and the ratchet component jointly form a ratchet mechanism.

In the utility model, the extension of the flexible rule is acted by the contraction mechanism and the ratchet mechanism, firstly, the spring is extended to the spring box by the movement of the sliding ring buckle, and the flexible rule is applied with a force contracting towards the spring box; and secondly, a force for stopping rotation is applied to the rotating component through the pawl component and the ratchet component. The two forces jointly form a force balance structure, when the flexible rule extends, the spring is enabled to extend outwards from the box, when the spring extends to the limit position, the traction force of the flexible rule further overcomes the resistance of the ratchet mechanism, the rotating component is enabled to rotate, and the flexible rule with a certain length is released; when the release, the clockwork spring is to the shrink in the box, and then drives the tape measure shrink, ensures the utility model discloses can not break away from with the trunk because of the extension of tape measure. The process is repeated circularly from the extension of the spring to the rotation of the rotating part to the contraction of the spring, and the continuity measurement of the tree is realized. At least one ratchet is arranged and evenly distributed in a ring shape by taking the axis of the central column as the center, and the ratchet is mainly used for adjusting the length of the tape released in each cycle.

Preferably, the bottom surface in the shell is fixedly connected with at least two fixing buckles, and the positions of the fixing buckles, which are in contact with the tape, are arranged at positions except for the tangent line of the tape outlet and the central column; the flexible rule passes through the fixed ring buckle; the sliding ring buckle and the fixing ring buckle are provided with rotating shafts at positions contacting with the tape, and the rotating shafts can rotate relative to the sliding ring buckle and the fixing ring buckle and can contact with the surface of the tape.

The rotating shafts arranged on the sliding ring buckle and the fixing ring buckle mainly convert sliding friction into rolling friction, so that the resistance of the tape on the sliding ring buckle and the fixing ring buckle is reduced. In addition, through arranging of slip latch closure, fixed latch closure, can form the assembly pulley structure in the holding intracavity for the effort that applys to the tape measure when amplifying the tree growth, even if the effort of release is very little when the tree growth, also can by the utility model discloses clear discernment arrives. The problem that the tree growth is limited due to the fact that the acting force cannot be prolonged when the flexible rule cannot identify the tree growth is avoided, and therefore growth deformity occurs and the accuracy of a measuring result is affected is solved.

Preferably, a circular through hole is formed in the shell cover, a circular vertical plate is arranged at the top of the second baffle plate, and the circular vertical plate extends to the outer side from the circular through hole and is fixedly connected with the knob component; the knob component comprises a third baffle plate, and a knob is arranged on the top surface of the third baffle plate; ratchet part, knob part all can take place relative motion with the cap, and ratchet part, knob part and cap are face contact, and the cooperation mode is interference fit.

The knob component is used for manually retracting the tape, and the tape cannot be retracted by singly depending on the structure because the ratchet mechanism can only rotate in one direction. In addition, the ratchet component, the knob component and the shell cover are in surface contact, the matching mode is interference fit, and when the flexible rule is extended, the rotating component can only be driven to rotate, and the frictional resistance among the ratchet component, the knob component and the shell cover cannot be overcome.

Preferably, a support plate is vertically arranged on the outer bottom surface of the shell, and the support plate is arranged at the edge of the shell; the supporting plate is arc-shaped.

The backup pad is circular-arc, and the purpose more can laminate the surface shape of trees, promotes the utility model discloses a stability.

Preferably, a cylindrical hinge is fixedly connected to the bottom surface inside the shell, a hinge hole is formed in the bottom of the rotating part, and the rotating part is movably connected with the shell through the cylindrical hinge; the spring barrel is characterized in that a positioning block is fixedly connected to the bottom surface inside the shell, a positioning channel is arranged at the center of the spring barrel, and the spring barrel is fixedly connected with the shell through the positioning block.

Preferably, a ruler hook is arranged on the side surface of the central column, and one end of the flexible ruler is connected to the central column through the ruler hook.

Preferably, the flexible rule is provided with a scale.

The utility model discloses following beneficial effect has:

1. the utility model discloses a balanced structure of a power is constituteed jointly to shrink mechanism and ratchet, from the extension of clockwork spring, to the rotation of rotary part, to the shrink of clockwork spring again, this process circulation is reciprocal to the realization is measured the continuation of trees.

2. The utility model discloses a slip latch closure and solid fixed ring detain the assembly pulley structure that forms in the holding intracavity, solved and be difficult to effectively discern the small strength when trees grow among the prior art, lead to trees to grow and take place sunken, deformity by measuring unit's influence, can lead to the fact the damage of not equidimension to trees, also can influence the technical problem of the accuracy of the data collected, through the effort of applying to the flexible rule when enlarging trees growth, promote measured data's accuracy.

3. The utility model discloses a circular-arc backup pad makes the utility model discloses the surface shape of trees can laminate promotes the utility model discloses a stability.

Drawings

Fig. 1 is a perspective view of the present invention.

Fig. 2 is an exploded view of the present invention.

Fig. 3 is a top view of the internal structure of the present invention.

Fig. 4 is a perspective view of the rotating member.

Fig. 5 is a cross-sectional view of the rotating member.

Figure 6 is a view of the ratchet member configuration one.

FIG. 7 is a second ratchet member configuration view.

Fig. 8 is a first structure view of the knob part.

Fig. 9 is a second structure view of the knob member.

Fig. 10 is a schematic view of the barrel and sliding buckle connection.

FIG. 11 shows a first structure of the sliding ring buckle and the fixing ring buckle.

FIG. 12 shows a second structure of the sliding buckle and the fixing buckle.

Reference numerals: 10-a housing; 11-a support plate; 12-flexible rule outlet; 13-flexible rule hook; 14 a-cylindrical hinge; 14 b-hinge holes; 15 a-a locating block; 15 b-positioning channels; 20-a shell cover; 21-a circular through hole; 30-a rotating member; 301-a central column; 302-a first baffle; 31-a pawl member; 31 a-a slider; 31 b-a slide; 31 c-spring; 31 d-spring seat; 32-a ratchet member; 321-a second baffle; 322-ratchet; 323-round riser; 33-a knob member; 331-a third baffle; 332-a knob; 40-barrel of spring; 41-spring; 51-fixing a ring buckle; 52-sliding ring buckle; 53 a-tape; 53 b-ruler hook.

Detailed Description

Example 1: as shown in fig. 1 to 12, a measuring sleeve with a slidable ring buckle includes a housing 10 and a housing cover 20, the housing 10 is fixedly connected with the housing cover 20 and encloses an accommodating cavity therein, a rotating member 30 is movably connected to a bottom surface inside the housing 10, and the rotating member 30 can rotate relative to the bottom surface of the housing 10; the middle part of the rotating component 30 is provided with a central column 301, and the side surface of the central column is wound with a flexible rule 53 a; a barrel 40 is fixedly connected to the bottom surface inside the shell 10, a spring 41 is arranged inside the barrel 40, the spring 41 is fixedly connected with a sliding ring 52 outside the barrel 40, and the sliding ring 52 can move relative to the shell 10; a tape outlet 12 is arranged on any side surface of the shell 10, and a tape 53a passes through the sliding buckle 52 and then extends to the outer side of the shell 10 from the tape outlet 12; the contact position of the tape 53a and the sliding buckle 52 does not fall on the tangent line of the tape outlet 12 and the central column 301; the opposite side of the side where the tape outlet 12 is located is provided with a tape hook 13, and the tape hook 13 can be detachably connected with a tape 53 a.

The utility model discloses in, the tape 53a extends to the device outside from tape export 12, encircles and is connected with tape couple 13 behind the trunk, through tape 53a, the utility model discloses can fix on the trunk surface, simultaneously, trunk growth drives outside tape 53a extension, and consequently accessible tape 53a carries out the persistence measurement to the trunk diameter. The rotary member 30 is mainly used for fixing and storing the tape 53a, and since the rotary member 30 and the housing 10 can rotate relatively, the tape 53a can be stored by clockwise or counterclockwise rotation of the rotary member 30. The barrel 40 and the slip ring 52 fixedly connected to the spring 41 form a reciprocating contraction mechanism, and when the tape 53a is extended due to the influence of tree growth, the slip ring 52 is driven to move, and further the spring 41 is driven to contract, so that the extension of the tape 53a outside the housing 10 needs to overcome the resistance generated by the spring.

Two end faces of a central column 301 of the rotating component 30 are respectively provided with a first baffle plate 302, and the area of each first baffle plate 302 is larger than that of the end face of the central column 301; a pawl part 31 is arranged on a first baffle plate 302 on the top of the central column 301, the pawl part 31 consists of a slide block 31a, a slide way 31b, a spring 31c and a spring seat 31d, the slide block 31a is movably connected inside the slide way 31b, the slide block 31a is connected with the spring seat 31d through the spring 31c, and the slide block 31a can relatively move on the diameter of the first baffle plate 302; the slider 31a is wedge-shaped.

The wedge shape of the sliding block 31a mainly means that the end of the sliding block 31a away from the center of the first baffle 302 is wedge-shaped, that is, there is an inclined surface, when the rotating component 30 rotates, so that the inclined surface of the sliding block 31a contacts with another inclined surface matched with the inclined surface, the sliding block 31a can move to the center of the first baffle 302 along the slide way 31b, and the spring 31c is compressed, and when the inclined surface passes by the other inclined surface, the sliding block 31a can be reset under the action of the spring 31 c.

The shell cover 20 is provided with a ratchet component 32, the ratchet component 32 comprises a second baffle 321, the bottom of the second baffle 321 is fixedly connected with at least one ratchet 322, and the ratchet 322 is annularly and uniformly distributed by taking the axis of the central column 301 as the center; when the spring 31c is in a free state, the slider 31a is engaged with the ratchet 322; the pawl member 31 and the ratchet member 32 together constitute a ratchet mechanism.

In the utility model, the extension of the tape 53a is affected by the combined action of the contraction mechanism and the ratchet mechanism, and firstly, the spring 41 is extended out of the barrel 40 by moving the sliding ring buckle 52, and a force contracting towards the barrel 40 is applied to the tape 53 a; secondly, a force resisting rotation is applied to the rotating component 30 through the pawl component 31 and the ratchet component 32. The two forces jointly form a force balance structure, when the tape 53a extends, the force balance structure is firstly expressed that the spring 41 extends outwards, when the spring 41 extends to the limit position, the traction force of the tape 53a further overcomes the resistance of the ratchet mechanism, so that the rotating component 30 rotates, and a certain length of the tape 53a is released; when the release, clockwork spring 41 contracts to the box, and then drives the shrink of tape 53a, ensures the utility model discloses can not break away from with the trunk because of the extension of tape 53 a. The process is repeated circularly from the extension of the spring 41 to the rotation of the rotating part 30 to the contraction of the spring 41, and the continuous measurement of the trees is realized. At least one ratchet 322 is arranged uniformly in a ring shape by taking the axis of the central column 301 as the center, and is mainly used for adjusting the length of the tape 53a released in each cycle.

The bottom surface in the shell 10 is fixedly connected with at least two fixed buckles 51, and the positions of the fixed buckles 51 contacting with the tape 53a are all arranged at positions except the tangent line of the tape outlet 12 and the central column 301; the flexible rule 53a passes through the fixing buckle 51; the sliding ring buckle 52 and the fixed ring buckle 51 are provided with rotating shafts at positions contacting with the tape 53a, and the rotating shafts can rotate relative to the sliding ring buckle 52 and the fixed ring buckle 51 and can contact with the surface of the tape 53 a.

The rotating shafts arranged on the sliding ring buckle 52 and the fixed ring buckle 51 mainly convert sliding friction into rolling friction, thereby reducing the resistance of the tape 53a on the sliding ring buckle 52 and the fixed ring buckle 51. In addition, through arranging of slip latch closure 52, fixed latch closure 51, can form the assembly pulley structure in the holding intracavity for the effort that applys to tape 53a when enlargiing the tree growth, even if the effort of release is very little when the tree growth, also can by the utility model discloses clear discernment. The problem that the tree growth is limited due to the fact that the acting force cannot be prolonged when the flexible rule 53a cannot identify the tree growth is avoided, and therefore growth deformity occurs and the accuracy of the measuring structure is affected is solved.

A circular through hole 21 is formed in the case cover 20, a circular vertical plate 323 is arranged at the top of the second baffle 321, and the circular vertical plate 323 extends to the outer side from the circular through hole 21 and is fixedly connected with the knob part 33; the knob part 33 includes a third barrier 331, on the top surface of which the knob 332 is disposed; ratchet part 32, knob part 33 all can take place relative motion with cap 20, and ratchet part 32, knob part 33 and cap 20 are face contact, and the cooperation mode is interference fit.

The knob member 33 is used for manually retracting the tape 53a, and since the ratchet mechanism itself can rotate only in one direction, the retraction of the tape 53a cannot be achieved by virtue of this structure alone. In addition, the ratchet member 32, the knob member 33 and the case cover 20 are in surface contact, and the fitting manner is interference fit, mainly when the tape 53a extends, the rotating member 30 can only be driven to rotate, and the frictional resistance between the ratchet member 32, the knob member 33 and the case cover 20 cannot be overcome.

A support plate 11 is vertically arranged on the outer bottom surface of the shell 10, and the support plate 11 is arranged at the edge of the shell 10; the support plate 11 is arc-shaped.

Backup pad 11 is circular-arc, and the purpose more can laminate the surface shape of trees, promotes the utility model discloses a stability.

A cylindrical hinge 14a is fixedly connected to the bottom surface inside the housing 10, a hinge hole 14b is formed in the bottom of the rotating component 30, and the rotating component 30 is movably connected with the housing 10 through the cylindrical hinge 14 a; a positioning block 15a is fixedly connected to the bottom surface inside the casing 10, a positioning channel 15b is arranged at the center of the spring barrel 40, and the spring barrel 40 is fixedly connected with the casing 10 through the positioning block 15 a.

A ruler hook 53b is arranged on the side surface of the central column 301, and one end of the tape 53a is connected to the central column 301 through the ruler hook 53 b.

The flexible rule 53a is provided with a scale.

The barrel 40 belongs to the prior art, and the specific design is numerous and will not be described in detail. In addition, the above-mentioned embodiments are only preferred embodiments of the present invention, and the scope of the present invention should not be limited thereto, so that the present invention is covered by the claims and the equivalent changes.

Claims (9)

1. The measuring sleeve with the slidable ring buckle comprises a shell (10) and a shell cover (20), wherein the shell (10) is fixedly connected with the shell cover (20) and an accommodating cavity is enclosed inside the shell, and is characterized in that a rotating part (30) is movably connected to the bottom surface inside the shell (10), and the rotating part (30) can rotate relative to the bottom surface of the shell (10); the middle part of the rotating part (30) is provided with a central column (301), and the side surface of the central column is wound with a flexible rule (53 a); the spring barrel (40) is fixedly connected to the bottom surface inside the shell (10), a spring (41) is arranged inside the spring barrel (40), the spring (41) is fixedly connected with a sliding ring buckle (52) on the outer side of the spring barrel (40), and the sliding ring buckle (52) can move relative to the shell (10); a tape outlet (12) is formed in any one side surface of the shell (10), and a tape (53a) penetrates through the sliding ring buckle (52) and then extends to the outer side of the shell (10) from the tape outlet (12); the contact position of the tape (53a) and the sliding buckle (52) does not fall on the tangent line of the tape outlet (12) and the central column (301); the opposite side of the side where the tape outlet (12) is located is provided with a tape hook (13), and the tape hook (13) can be detachably connected with a tape (53 a).

2. The measuring sleeve with the slidable buckle according to claim 1, wherein the two end faces of the central column (301) of the rotating component (30) are respectively provided with a first baffle (302), and the area of the first baffle (302) is larger than that of the end face of the central column (301); a pawl part (31) is arranged on a first baffle plate (302) at the top of the central column (301), the pawl part (31) consists of a sliding block (31a), a sliding way (31b), a spring (31c) and a spring seat (31d), the sliding block (31a) is movably connected inside the sliding way (31b), the sliding block (31a) is connected with the spring seat (31d) through the spring (31c), and the sliding block (31a) can relatively move on the diameter of the first baffle plate (302); the sliding block (31a) is wedge-shaped.

3. The measuring sleeve with the slidable buckle as claimed in claim 2, wherein the case cover (20) is provided with a ratchet member (32), the ratchet member (32) comprises a second baffle (321), the bottom of the second baffle (321) is fixedly connected with at least one ratchet (322), and the ratchet (322) is annularly and uniformly arranged by taking the axis of the central column (301) as a center; when the spring (31c) is in a free state, the sliding block (31a) is meshed with the ratchet (322); the pawl component (31) and the ratchet component (32) jointly form a ratchet mechanism.

4. The measuring sleeve with the slidable ring buckle as claimed in claim 3, wherein the bottom surface inside the housing (10) is fixedly connected with at least two fixed ring buckles (51), and the positions where the fixed ring buckles (51) are in contact with the tape (53a) are arranged at positions other than the tangent of the tape outlet (12) and the central column (301); the flexible rule (53a) penetrates through the fixing ring buckle (51); the sliding ring buckle (52) and the fixed ring buckle (51) are respectively provided with a rotating shaft at the position contacted with the tape (53a), and the rotating shafts can rotate relative to the sliding ring buckle (52) and the fixed ring buckle (51) and can be in surface contact with the tape (53 a).

5. The measuring sleeve with the slidable ring buckle as claimed in claim 4, wherein the case cover (20) is provided with a circular through hole (21), the top of the second baffle (321) is provided with a circular vertical plate (323), and the circular vertical plate (323) extends from the circular through hole (21) to the outside and is fixedly connected with the knob component (33); the knob component (33) comprises a third baffle plate (331), and a knob (332) is arranged on the top surface of the third baffle plate (331); ratchet part (32), knob part (33) all can take place relative motion with cap (20), and ratchet part (32), knob part (33) and cap (20) are face contact, and the cooperation mode is interference fit.

6. The measuring sheath with the slidable clasp according to any one of claims 1 to 5, wherein a support plate (11) is vertically arranged on the outer bottom surface of the housing (10), the support plate (11) being arranged at the edge of the housing (10); the supporting plate (11) is arc-shaped.

7. The measuring sleeve with the slidable buckle according to claim 6, wherein a cylindrical hinge (14a) is fixedly connected to the bottom surface inside the housing (10), a hinge hole (14b) is formed in the bottom of the rotating component (30), and the rotating component (30) is movably connected with the housing (10) through the cylindrical hinge (14 a); the spring barrel is characterized in that a positioning block (15a) is fixedly connected to the bottom surface inside the shell (10), a positioning channel (15b) is arranged at the center of the spring barrel (40), and the spring barrel (40) is fixedly connected with the shell (10) through the positioning block (15 a).

8. The measuring sleeve with the slidable ring buckle as claimed in claim 7, wherein a ruler hook (53b) is arranged on the side surface of the central column (301), and one end of the flexible ruler (53a) is connected to the central column (301) through the ruler hook (53 b).

9. Measuring sleeve with slidable clasp according to claim 8, characterized in that the flexible rule (53a) is provided with graduations.

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